Pure and metal oxide doped nanocrystalline ceria has been prepared by the hydrothermal technique,and the samples annealed at different temperatures to study the interaction between dopants and the ceria.The results indicated that CdO enhanced the growth of ceria particles while Al2O3 and ZrO2 hindered it.MgO,CaO,SrO and BaO only hindered the ceria particle growth at lower temperatures.At higher temperatures,as the impurity phases crystallized,they no longer hindered the growth of ceria particles.